The present invention relates in general to a method and an apparatus for controlling a polymerization reaction, and particularly to those in which an optimum polymerization reaction is attained by temperature control.
When organic polymers are produced by a suspension polymerization, an emulsion polymerization or the like, the particle sizes of polymers formed with a lapse of time must in general be as uniform as possible. This is because the physical and chemical properties of organic polymers produced under the conditions of polymerization in which the distribution of the particle sizes is wide are considerably inferior to those of organic polymers produced under the conditions in which said distribution is narrow.
When rubber is produced by emulsion polymerization, for instance, the particle sizes are determined primarily dependent on the fluctuations in the quantity of an emulsifying agent and the temperature of polymerization. Even when the quantity of the emulsifying agent is fixed, therefore, the particle sizes of the produced polymers are varied by the fluctuation of the temperature during the process of polymerization, which results in the deterioration of the quality of the rubber.
Conventional temperature controls are carried out manually on the basis of the data of experiments which were previously performed. This often necessitates complicated valve operations and the like. Even with complicated valve controls, temperature control is not fine enough to achieve the desired result.
There is another proposal for temperature control in which temperature is adjusted on the basis of the rate of polymerization which is known by measuring the density of the solids content of a polymer liquid. According to this proposal, however, temperature control cannot be performed promptly and it is difficult to automate the control of the polymerization reaction. A sample is manually taken from a reactor for measuring the rate of polymerization. Then, temperature is adjusted after the sample is analyzed and the rate of polymerization is determined. In addition, this proposal cannot ensure fine control of temperature, which in turn causes non-uniformity of particle size and the consequent deterioration of polymer quality.
Furthermore, for the purpose of reducing the time required for measuring the rate of polymerization, a method has been proposed in which the rate of polymerization is measured from the refractive index of an emulsion in the reactor (ref. the Official Gazette on Japanese Patent Laid-Open No. 58-206602). According to this proposal, it is necessary also to take out the emulsion from the reactor, which would put restrictions on the installations especially when the emulsion is unstable.